Rubber roll-up doors for industrial and commercial use have been known for some time. An example is disclosed in U.S. Pat. No. 4,478,268 to Palmer issued Oct. 23, 1984. A primary advantage of a door of this type which is made from a rubber curtain is that it is designed to withstand an accidental impact from a vehicle or other object while standard doors of other types (such as steel doors) will often be destroyed or cause damage to the impacting object.
In order to reduce the likelihood of tearing of the rubber door upon impact, it is desirable that the door be capable of disengaging from the door frame upon impact. U.S. Pat. No. 5,392,836 to West et al., issued Feb. 28, 1995 teaches a rubber door with its vertical side edges insertable into door guides positioned adjacent each vertical side of the door. Mounted along the vertical edges of the roll-up door are a number of hemispherical follower elements which are spaced apart from one another and vertically aligned. These elements are bolted to the edge of the door, and are made of hard plastic material or some other compressible material. The vertical sides of the door are inserted in the door guides, each guide forming a narrow gap through which the vertical edges of the door may be inserted. These guide members have tapered portions that form a tapered inward section which allows for a wedging action by the follower elements causing the guide to open up and release the door edge under impact conditions.
U.S. Pat. No. 5,964,270 to Kirkey et al., issued Oct. 12, 1999 teaches the use of thickened edges along the vertical side edges of a roll-up type door, which are insertable in spaced apart guide channels, positioned along the vertical sides of the frame of the door. A sloping shoulder is formed where each side edge section meets the thinner main area of the door. Friction reducing wear resistant fabric strips are bonded to both of the side edge sections and extend therealong. The thicker side edges are designed to be pulled from the guide channels under impact forces.
It is known also to provide a weighted bottom bar attached to the bottom edge of roll up doors, designed to assist in the raising and lowering of the door and to minimize damage to the door structure during accidental collision therewith. For example, U.S. Pat. No. 5,025,847 to Mueller, issued Jun. 25, 1991 discloses a bottom bar connected to tensioning means located in door guides and that are connected to horizontal tabs mounted on the bottom bar. The bottom bar includes vertically extending U shaped brackets and a sliding block assembly mounted therebetween. The block assembly has interlocking portions which are connected together by dove tail connectors. A shear pin extends through a passage extending through the dove tail connector. An impact to the bottom bar causes the shear pin to be sheared off, thereby permitting release of the section of the bottom bar connected to the curtain.
U.S. Pat. No. 5,139,074 to Warner, issued Aug. 18, 1992 discloses a bottom bar attached to a roll down door composed of superimposed strips of resilient material such as rubber and metal strips. Each end of the bottom bar is provided with a longitudinal open-ended slot and an extension of the bottom bar is mounted within each slot in a manner such that the extensions can slide freely in the slots in a direction parallel to the plane of the door. These extensions will release from the slots if the bar is subjected to an accidental impact.